Recording of data



April 1l, 1967 K. G. H-UNTLEY RECORDING oF DATA 5 Sheets-Sheet 1Original Filed March 31, 1959 April 11, 1967 k. G. I-IuNrLI-:Y 3,313,883

RECORDING OF DATA Original Filed March 5l, 1959 5l Sheets-Sheet 2 INPUTDEVICE LOGIC 'OF FIG. I

w BI STABLE 5o HORIZONTAL ADDRESS HORIZONTAL INPUT I cDINcIDENcE UNIT sal l VERTICAL ADDRESS VERTICAL mfp coINcIDENcE Fmg. 2

April11, 1967 K. G. HUNTLEY RECORDING 0F yDATA original Filed March 31;1959 5 Sheets-Sheet 3 REGISTER VERTICAL ADDRESS E NCODER a O o o o PLUGCONNECTING BoAR DECODER 5 'sheets-sheet 4 iginal Filed March 31, 1959April 11, 1967 K. G. HUNTLEY 3,313,883

,RECORDING oF DATA- Original Filed March 3l, 1959 l 5 Sheets-Sheet V5X-AXIS DIFF Y-AXIS DIFF QR. 2 was XEROGRAPHIC DRUM INT EGRATOR ZOOUnited States Patent O 3,513,883 nnconnrno on DATA Keith Gordon Huntley,Alexandria, Va., assigner torThe This invention relates to a printer ofalpha-numeric and other symbols forming, for example, the decoded outputof a digital machine, the printer being of the type in which the outputis visually displayed and optically projected upon ya moving lightsensitive recording surface.

The present application is Aa continuation of my copending application,Ser. No. 803,210, led Mar. 3l, 1959, now abandoned. v

Alpha numeric and other symbols and line patterns generally arehereinafter referred to as characters.

It has been proposed to display the output of Ia digital machine indecoded alpha-numeric form upon the screen of a cathode ray tube and toproject the display by optical means upon a rotating xerogr-aphic drumfor the purpose of obtaining therefrom la permanent xerographic print ofthe output on a continuous paper web transported in contact with thedrum. The main advantage of such a scheme, when compared with theconventional electromechanical output printer, is the vastly higher rateof printing which is made possible by the elimination of mechanical typebars land the like. The xerographic process is in f-act a form of dryphotography, which combines to a great extent the advantages of thelight sensitive emulsions without the complications of Wet developing,fixing, and drying.

The former proposal discloses in particular how a line-up of charactersmay be displayed upon the screen of a cathode ray tube upon selectionthrough the input code of pairs of electrical lines sequentiallycorresponding to the succession of characters displayed, and details themanner in which the line-up of characters is vertically controlled inrelation to the rate of the input code and to the movement of thexerographic surface, so as to ensure parallel lines of printed output`free from yslanting relatively to the longitudinal axis of thepaper'web. It relies, in particular, on synchronizing input ysignals tocontrol either the vertical stagger of the characters displayed or thespeed of the drum. It does not disclose any provision for selctivelycontrolling the location of printing vertically and horizontally or/ andfor printing at any drum speed independently of the incoming rate of theinput code. t

One object of the present invention is to provide a printer of the typeas hereinbefore defined, wherein relative movement between projectedcharacters and sensitive surface is eliminated so as to produce lines ofprinting at right angle to the direction of motion of said surfaceindependently of the incoming rate of the input code..

One outstanding advantage in the realization of the above object is thatthe sensitive surface may be arranged to move at any desired rate tosuit printing requirements and each displayed character willautomatically assume the vertical positioning required for ensuringlinesL of printing free from slant. f

A further object is to provide a printer wherein the display iscontrolled so as to enable anyV one character to be printed at anydesired location upon a print receiving medium under the control of theinput code or the logics of the printer.

The above object points to an essential requirement for a trulyuniversal printer, particularly where printing upon standard formsrequiring entries at a variety of horizontal and vertical locations isrequired.

3,313,883 Patented Apr. l1, 1967 ice A more particular object of theinvention is to provide an improved system or print for recordingalpha-numeric and similar characters which comprises a device xforforming a particular standard image of such characters selected, forexample, from a store of standard images each with -a selected fixedarrangement of such characters, another device for forming a secondimage of such characters from variable arrangement of the charactersgenerated in response to input signals, and means for projecting thestandard image and the second image substantially simultaneously upon amoving light sensitive surface, the characters forming the second imagebeing located in the appropriate position relative to the charactersforming the standard image. The standard image can be, for example, aphotographic image of an insurance form, and the second image can be forexample, the name of the insured as well as other variable informationwhich is to be printed together with the insurance form. The inventionconsists therefore of a printer for recording the charactershereinbefore defined from a display thereof set up in response to codedinput signals representing said characters, comprising means whereby thedisplay is projected onto a light sensitive recording surface in motionand is so controlled as to eliminate relative movement between eachprojected character and said surface, Whatever the rate of said motion,and independently of the incoming rate of the input signals.

The invention also consists of a printer for recording the charactershereinbefore defined from a display thereof set up in response to codedinput signals representing said characters comprising means whereby thedisplay is projected onto a light sensitive recording surface in motionand is so controlled as to eliminate relative movement between eachprojected character and said surface, whatever the rate of said motionand independently of the incoming rate of the input signals, and meansfor causing any one character to be projected at any one desiredlocation upon said recording surface, so as to form thereon a detectableimage thereof.

Preferably, the input coding is binary, the display of images is set upupon the screen of a cathode ray tube, and the light sensitive recordingsurface is Aa xerographic surface.

It rnust be understood, however, that other digital codings, equivalentdisplays and light sensitive recording surfaces may be used for the`realization of the invention.

In the embodiments presently to be described, the use of a xerographicrecording surface arranged upon a rotating drum will be disclosed, thedisplay optically -projected-thereon forming electrostatic latentimages, which after development by electroscopic powders are convertedinto corresponding powder images to be transferred and xed onto aprint-receiving medium, such as a web of paper, transported in contactwith the drum at the same rate as the peripheral speed thereof.

The use of a xerographic endless belt instead of a drum would constitutean obvious alternative.` v

Similarly, the xerographic surface may be arranged as a coating to Vaweb, such yas a paper web, in which case the powder images need not betransferred to a printreceiving medium, the coated web forming in factsaid medium and the powder images being fixed thereto.

A further alternative is the transfer on to -a dielectric web of theelectrostatic images formed on the xerographic surface, development andxing takin-g place on the dielectric web.

The xerographic process is by now a well established art and no detaileddescription thereof is thought necessary. A brief reference will be madethereto later in the specification.

It is obvious to the skilled in the art that the xerographic surfacearranged as a coating on drum, belt, or web, as

indicated, could be replaced by a photographic emulsion similarlyarranged.

In regard to preventing relative movement between projected charactersand moving recording surface, this is preferably arranged by sensing therate of motion of said recording surface for the purpose of derivingtherefrom a rate signal effective in causing an electrical output risinglinearly from a datum value with a slope finally governed by said rate,said output being operative to control the relative vertical positioningof the characters displayed, so as to cause them to be projected in aline free from slant upon the moving recording surface.

Preferably, the rate signal is fed to an integrator, the output of whichis fed through an amplifier to the Ivertical deflection means of acathode ray tube upon which the characters are displayed, said outputbeing effective in controlling the vertical stagger of each characterrelatively to the preceding character, with the exception of the firstcharacter.

The cathode ray tube, which may be of the electrostatic orelectromagnetic deflection type, is `associated with a charactergenerator capable of converting the digital output of, say, a computingdevice, into X and Y deflection waveforms for causing the beam of thetube to write the corresponding character upon the screen in conjunctionwith Z or blanking waveforms derived from either the X or Y waveforms.

The generator may be, for example, of the type described in a copendingapplication Serial No. 753,685 led Aug. 17, 1958, in the name of AdamChaimowicz, now U.S. Patent No. 3,024,454 granted Mar. 6, 1962.

The character generators described in the above applications areintended for spot-sequential display of characters, wherein eachcharacter is dened by a succession of light dots, the successivepositioning of each dot being determined by simultaneous X'and Ydeflection waveforms.

Thepresent invention however is not intended to be limited to this typeof display, an obvious alternative being the full-trace type of display.

The character generator is fed from a character selection matrixyielding a unique output line for 'any one combination of digital inputsignals, each output line representing one character and causing thegeneration of the corresponding X and Y deflection waveforms.

The characters are displayed upon the screen of the cathode ray tube inat least one line-up and the display is so controlled as to allow thecharacters to be printed at any desired transversal or longitudinallocation upon the print-receiving medium, say, a paper web cooperatingwith a xerographic drum, both in response to coded input signals 'aloneor in conjunction with pre-set combinations within the printer.

The location of any one character upon the print-receiving medium isdefined by its horizontal printin-g position or horizontal recordingaddress, and by its vertical printing position, or vertical recordingaddress.

It is clear that the horizontal recording address is determined by thecorresponding display position of the character along the line-up, orhorizontal display address, and the vertical recording address by theline in which the character is printed.

One way of controlling the location of printing is achieved byrecurrently generating step by step all possible horizontal displayaddresses and inhibiting character generation correspondingly to therecording addresses where noprinting is required.

L Thus assuming, for example, that it is arranged that one line ofprinting. shall contain a maximum of 100 character positionsequidista-ntly spaced and that the drum is allowed to rotate of drum`circumference before one line is commenced, this bein-g, therefore, theline-space unit, and that 1/10" is the height of a character, printingis potentially possible in approximately four lines per inch of drumcircumference giving 100 4 character positions.

Horizontal location of printing is obtained b-y inhibiting charactergeneration, and, therefore, display, at certain horizontal displayaddresses of the beam of the cathode ray tube. lf, for example, it isrequired to indent three spaces at the beginning of a line, the beamwill be allowed to go through three horizontal display addresses withouta character bein-g generated and displayed. Character generation may fbeinhibited for instance by feeding through the input a coded word causingselection of an unconnected line through the character selection matrix.

The vertical recording address clearly involves selection of-therequired line. This is achieved by preventing commencement of a line ofdisplayed characters until Va given num-ber of line-spacing units havebeen counted. Thus, if it is desired to print at the middle of the fifthline, no line ofcharacters will be allowed to commence until the fourthline-spacing has been counted and then generation will be inhibiteduntil the beam of the cathode ray tube has reached the 50th horizontalcharacter display address.

The horizontal display addresses may be associated Y with a binaryVregister in such manner that successive states correspond to successiveaddresses and cause corresponding binary outputs from the register.Similarly for the vertical recording addresses.

Thus, the horizontal and vertical recording addresses of a character areeach represented by the state of the corresponding register, the state 0representing the beginning of the line, in the one case, and the firstline in the other.

The output corresponding to each state of the register conforms to thebinary number which the state represents. Thus assuming, for example, aregister comprising seven lbistable stages, the state corresponding tothe binary number 0000001 will produce the following output combinationon seven distinct lines: no-pulse, no-pulse, no-p-ulse, no-pulse,no-pulse, no-pulse, pulse, the combination identifying one definitecharacter position.

By arranging inhibition of character generation until the output of thecharacter address registers coincides with pre-set combinations set upfor instance in similar registers, printing may be effected at anypredetermined location upon the print-receiving medium.

Summing up on the broad concept of character inhibition for the purposeof controlling location of printing, two :distinct provisions areincluded in one aspect of the invention, (a) inhibition through thecoded input, (b) inhibition through pre-set combinations.

Let us assume for instance that lines of characters have to be enteredat various locations upon forms. The

spacing required between Igroups of characters forming one entry wouldbe controlled through the coded input, independently of pre-setcombinations, whereas the horizontal and vertical location of the entryupon a form would be controlled through sets of predeterminedcombinations.

Printing at predetermined recording addresses will heresistsin arrangingmatters so that the beam of the cathode ray tube is shifted directly tothe display address called for. Assuming, for instance, that the singleword Paid is to be entered in one line, it may be advantageous to sweepthe bea-m directly to the display address correspondingto the horizontalrecording address in which the letter P is to 'be printed without havingto shift the beam step-wise through the display addresses precedingletter P. Once the display address corresponding to letter P isgenerated, the step-wise control is resumed in respect of letters a, i,and d. Should a further entry be required on the same line, the firsthorizontal display address will again be directly and the followingdisplay addresses. step-wise.

The direct generations of lhorizontal'display addresses is particularlyuseful when entering information upon standard forms according to aselectable range of pre-set layouts, i.e., tabulating. The directgeneration may be achieved by adapting any one of a range of horizontaltabulating orders issuing from the input to cause a combination to beset up in a binary register which through digital-to-analogue conversionproduces the analogues signal ensuring the X shift at'the cathode raytube corresponding to the desired display address.

The range of the horizontal tabulating orders to be accommodated is asuitable percentage of the maximum number of character positions in oneline.

The facility for direct generation of the horizontal display addressmust clearly be extended to all possible line positions, and this isachieved by cross-connecting means, such as plug-boards, as will beexplained hereinafter.

It will be appreciated that the direct generation of the horizontaldisplay address is made possible by the inertialess nature of theelectron beam of the cathode ray tube. The inertia of the xerographicdrum or its counterpart prevents a similar approach in the verticalrecording address generation in response to vertical address orders,since it is not possible to accelerate the drum instantaneously to thedesired position. The vertical address orders, therefore, are operativeonly in ensuring that the required time has passed for the drum to havemoved to the angular position corresponding to the line or verticalrecording address in which printing is required. A plug-boardarrangement similar to that associated With the horizontal displayaddressing may be employed.

If need be, a set of horizontal and vertical plug-boards may beincluded, the logics being adapted to call the pair required at anytime.

The printer to which `this invention is directed is intended to enableinput data in the form of coded alphanumeric and other symbols to betranslated into visible images to be printed on a print-receiving mediumat any desired location in response to orders emanating from the inputsource along withthe input data, or from within the logics of theprinter which may be aptly referred to as an electronic printer.

In addition to vertical and horizontal address orders, there will begenerally provided other orders such as Line Feed and Carriage ReturnOrder, Figure Shift and Letter Shift Order, Stop, Blank orders, and soforth. In the description of the practical embodiments which follows themode in which such orders are arranged will be made clear and it will beseen that many other desired orders may be accommodated along the linesdisclosed.

The input to the printer may be derived directly from a computer deviceor through any suitable recordingv medium such as magnetic tape,perforated tape and the like.

Where the input is from a recording medium which must be transportedpast a reading head, the rate of dis- `play of characters on the cathoderay tube is tied to said medium or may be ymade independent of saidmedium.

Assuming the use of tape for both alternatives of operation, in thefirst case the sprocket or clock pulse rate of the tape is limitedbetween the maximum permitted by the repetition rate of the charactergenerator, and the minimum ensuring display of a full line ofcharacters. In the second case, the input is read into a buffer storageat a rate which is governed by an internal clock which far exceeds thecharacter repetition rate. From the buffer storage the information isread out by the printer and displayed.

The use of a buffer storage and internal clock enables a betterutilization of the high printing speed of which the machine is capableinasmuch as variations in input rate are avoided, said input rate beingraised at all times to the maximum permitted by the character repetitionrate.

In short, the printer provides for the yfollowing controls andfacilities in combination or in any desired and convenient selection:

(l) Printing in slant-free lines regardless of the rate at which thelight sensitive surface is being moved and independently of the rate ofthe incoming signals constituting the input of the printer.

(2) Line-by-line printing -with word spacing controlled by the input andline spacing controlled by means actuated through motion of the lightsensitive surface relative to the display, for instance throughphotosensing marks on print medium or through a tachometer connected tothe rotating drum.

(3) Tabulating, horizontally and/or vertically according to pre-setcombinations in response to tabulating orders issuing from the input orfrom the logics of the system; if need be, said combinations being madeselectable in conjunction with the particular form in use out of aselectable range of forms, if printing upon forms is adopted.

(4) Tabulating horizontally and/or vertically according to tabulatingorders issuing from the input or the logics of the system and actingindependently of pre-set combinations.

(5) Step-by-step generation of horizontal character display addressescombined with character inhibition to produce horizontal and verticaltabulating.

(6) Direct generation of the character display address corresponding toa horizontal tabulating address, stepby-step generation of succeedinghorizontal character display addresses combined with characterinhibition for vertical tabulating. l

(7) Direct read in from input medium at a rate gov erned by the medium.

(8) Read in through buffer storage cooperating with high speed internalclock.

(9) Low speed and high speed rejection of information not conforming topre-set tabulating combinations through (7) and (8) respectively.

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings, wherein:

FIG. 1 is a functional diagram of printer logics.

FIG. 2 is a functional diagram of a mode of tabulating control.

FIG. 3 is an elaboration of FIG. 2.

FIG. 4 is a functional diagram of further printer logics.

FIG. 5 is a functional diagram of the arrangement for controlling thevertical display position of successive-characters to ensure slant-freelines of printing.

The arrangement referred to under FIG. 5 will be described last, sinceit forms as entity distinct from the actual printer logics insofar asresponse to coded input is concerned. Moreover, the arrangement iscommon to all the embodiments.

In FIG. l, a character generator 1, for instance of the type describedin either of the two above mentioned copending applications, is shownsupplying X and Y deflection waveforms to a cathode ray tube 2, throughdeliection amplifiers 3 and 4, for the purpose of displaying thecharacters selected by the character selection matrix 5 in response to adigitally coded input on input lines 6, said input representing forinstance, the output of a computing device.

The characters are formed each as a series of light dots with the aid ofa sequential pulse generator 7 and are sequentially displayed in atleast one -line-up which is optically projected through a lens systemrepresented at 8 on to a xerographic drum 9, the resulting electrostaticimages being subsequently adapted to be developed and printed upon aprint receiving medium say, a paper web (not shown), in a conventionalxerographic manner.

The xerographic drum consists of a metal drum on the surface of which aphotoconductor having a high dark resistivity, say, of the order of 1013ohm-centimetre is disposed in a uniform layer of a convenient thickness,usually ranging from a few microns to about 200 microns. Whileunexposed, the layer is charged to a potential of a few hundred volts.Upon exposure to a pattern of light, the areas upon which light hasfallen become relatively conductive and the charge thereon leaks away,the result being an electrostatic pattern or image corresponding to thelight image. The electrostatic image is subsequently developed byallowing chargeable particles charged to an opposite sign to come incontact therewith, whereby said particles will adhere by electrostaticattraetion only to the charged image areas. Where, as in our presentcase the original is a negative, i.e., the displayed characters emitlight and it is desired to print a positive copy the powder is chargedto the same sign as the layer and upon development is repelled by allexcept the image areas to which it is attached by virtue of its charge.After development the powder is transferred to a print receiving medium,for instance, the paper web referred to above, by establishing anelectrostatic field transversally of paper and layer with polarityarranged so as to cause the powder to leave the layer and be attractedto the paper.

The xerographic process is amply described in United States Patent No.2,297,691.

A horizontal display-address register is shown at 10 and a verticalrecording-address register at 11. Associated in rotation with thexerographic drum is a pulse tachometer 12 feeding into a pulse counter13.

In operation, with both registers set to zero, a line` action pulse online 14 derived from a line start signal on line 15, the origin of whichwill be indicated later, is routed through bistable 16 and causes a setpulse to be propagated through the sequential pulse generator 7 which,in the absence of inhibition, cooperates in displaying the characterselected by the selection matrix 5.

The set pulse does, in fact, activate the sequential pulse generator toa timing .set by the dot clock 17 through bistable 18. Gate 19 servesthe purpose of ensuring that bistable 16 is re-set at a clock time otherthan that in which a set pulse occurs.

The dot clock, which in a convenient embodiment may be in the form of amultivibrator is also effective in setting the instant when the beam ofthe cathode ray tube is to be switched on coincidently with. thegeneration of the Y deflection signal of one dot. As shown, the dotclock output is passed. through a pulse shaping and gating arrangementcomprising pulse )delaying units 20 and 21 in addition to and gates 22and 23, the output of said gates being combined in or gate 24. Theoutput of gate 24 determines the actual instant when the Y deilectionsignal corresponding to one dot is allowed through and gate 25 to switchon the beam, for instance, by raising the grid of the cathode ray tubeabove a cut off bias potential through amplifier 26.

The X and Y deflection waveforms are available through or gates 27 and28 respectively in a manner which has already been described in thecopending applications referred to.

It will be noted that the Y signals are branched off through unit 42 inaddition to being applied to deection amplifier 3, so as to control thebeam in the manner indicated above. Unit 42 allows an output pulse onlywhen the input pulse is greater than a predetermined amount. This is toensure that spurious signals are ignored.

It is assumed that the character selection matrix indicated in FIG. l isof the type including magnetic cores requiring a switching pulse. Theswitching pulse is provided in association with the lirst two stages ofthe se-y quential pulse generator through or gate 29 and amplier 30.

The foregoing description relating to FIG. 1 indicates the manner inwhich a line action pulse on vline 14 is operative in setting olf thesequential pulse generator 7 '8 which causes the character generator 1to make available at gates 27 and 28 the deflection waveformcorresponding to the character selected by the coded input combinationfed into character selection matrix 5 on lines 6, the timing being setby dot clock 17 which also controls the timing of beam bright up.

The pulse issuing from the last stage of the sequential pulse generator,when the dot-sequential formation of a character has been completed, isfed to horizontal displayaddress register 10, which in the presentembodiment comprises six bistable stages. Register 10, therefore,changes its state from 000000, representing the rst horizontaldisplay-address, to 00000l, representing the second horizontaldisplay-address. The output corresponding to this state is fed to adigital-toanalogue converter 31 wherein it is converted into theanalogue potential which extendedV to the cathode ray tube through thedeiiection amplifier 4 produces the required horizontal shift of thebeam to the second display-address.

The pulse issuing from the last stage of the sequential pulse generatoris, in addition, extended through thepulse shaping device 32, monostable33, and gate 34. Device 32 produces an output at the end of a pulse andmonostable 33 is arranged to have a predetermined operating time. Ifgate 34 is uninhibited, the pulse issuing therefrom will set bistable 16and a new pulse will be fed through to the sequential pulse generator inthe same manner as if a line action signal had occurred.

It is thus clear that as long as gate 34 is uninhibited characters willbe displayed sequentially. Gate 34 is, in fact, uninhibited as long asregister 10 is in a state other than 000000, since the output lines ofregister 10 are extended to or gate 35 the output of which conditionsand gate 34. The state 000000 does in fact occur at the end of a linewhen the register re-sets itself. The next line will not start untilanother line action signal is received.

Before the next line can be printed, however, a line spacing isrequired. This is arranged with the cooperation of pulse tachometer 12and pulse counter 13. Tac-hometer 12 is adapted to generate a givennumber of pulses per angular displacement of the drum corresponding tothe chosen line-spacing unit.

It is obvious to the skilled in the art that tachometer 12 may bereplaced by an arrangement for-sensing for instance, photosensing-spacedmarkings on the periphery of the drum, on the printreceiving medium, oron a member in rotational relation to the drum. Alternatively, magneticsensing may be used.

It is assumed in this embodiment that the number of pulses per linespacing is sixteen. Counter 13 is adapted to count line-spacing units,it will therefore emit one pulse per unit, i.e., a pulse every sixteentachometer pulses. The output from counter 13, which is shown ascomprising four bistable stages, provides the line start signal whenunit line-spacing has been established by allowing the drum to rotatethe requisite angular amount before the second line is commenced. Theline start sig* ual is applied through device 36 arranged to go off atthe beginning of a pulse.

As described so far, the arrangement is capable of producing evenlyspaced lines of printing, any spacing required within a line beingsecured by feeding the combination 000000 to the selection matrixthrough the coded input, this resulting, for example in the selection ofan unconnected character line, such as 37, and, therefore, in nocharacter forming signals being fed to the cathode ray tube.

Provision must obviously be included for marking off pages when printingfor instance upon continuous stationery, which may be arranged as aseries of business forms. This is accomplished by means of aphotoelectric pick-ofi 39 cooperating with a light control marking onthe stationery in use, which sends a re-set pulse to all registers, the

9 marking coinciding with the end or beginning of a page or form.

Alternatively, magnetic-marking and sensing may be resorted to for thesame purpose.

The cathode ray tube display may be in a form of a double line-up ofcharacters. In this case, the two lineups are disposed one over theother and the provision for shitting from the uppermost to the lowermost and vice Versa is secured through lthe addition to register 10 of afurther bistable stage 40. When the first line-up has been completed,the pulse shifting out of register 10 into bistable 40 causes the latterto apply to the cathode ray tube the shift potential required fordisplacing the beam to the second line-up p-osition. The shift potentialis applied -through line 41extended to Y amplifier 3. At the same timebistable 40 through gate 35 causes register 10 to go through a furthercycle, with the result that the characters readout will be displayed inthe lowermost line-up. The action as described of the additional stage40 is cancelled when the latter line-up is completed, conditions beingthus restored for the display of the upper line-up.

The two line-ups are intended to be projected onto the xerographic drumside by side so as to combine into a single line of characters. Comparedwith the single lineup, this arrangement enables a better utilization ofthe cathode ray tube width andof the available light output.

The provision for printing at any desired location upon theprint-receiving medium in response to pre-set cornbinations, i.e.predetermined tabulating, will now be described.

The output pulse from counter 13, apart from providing the line startsignal, causes in addition the operation of vertical recording-addressregister 11 which effectively counts the number of lines in theembodiment shown comprises seven bistable stages. At the end oi thefirst line of characters said register will therefore change its statefrom 0000000 to 0000001 and will continue to shift one binary step atthe end of each line until it resets to zero.

From each stage of both register 10 and register 11 an output line isextended, thus forming lines A and lines B. From the foregoing it isclear that the output combinations on said lines reflect at any instanta definite horizontal display address and a deiinite vertical recordingaddress.

With reference to FIG. 2, lines A are fed to coincidence circuit 50 towhich pre-set combinati-ons are also fed on an identical number of linesfrom horizontal address input unit S1. Upon coincidence between thecombination occurring on lines A and the combintaion set up in i a pulseis produced by coincidence 50.

Similarly for the vertical arrangement, lines B being associated withcoincidence 52 and vertical address input unit 53.

Where no control in response to combinations pre-set in S1 and 53 isrequiredsuch being the case when full lines are printed with unitline-spacing--a sequential display of characters proceed in the normalmanner, gate S4 being uninhibited and allowing a character code set-uptiming pulse originating from the sequential pulse generator to causethe next character to be read oir from the input 55.

The character code set-up timing pulse corresponds to that available online 33 in FIG. 1.

Where control is desired a set horizontal address pulse is fed tobitsable 56 which via or gate 57 inhibits gate 54 thus preventingfurther character read-out until a pulse from coincidence 50 re-setsbistable 56. Similarly for the control of the vertical address, inregard of which it should be noted, however, that only multiples of theline-'spacing unit may be prearranged. Unit 5t) is the counterpart of56.

In FIG. 2 block 58 represents the logics of FIG. l.

It will be manifest to the skilled in the art that where iti it isintended that the tabulating order should be operative independently ofpre-set combinations, units 51 and l 53 need only be in the form ofbinary registers, the tabulating order issuing from the input includinga binary number marking the address required.

In general, pre-set combinations in the manner referred to will beusefull where predetermined horizontal and vertical tabulating layoutsare required in conjunction with printing upon .a range of standardfor-ms. T o this end, the address input units may be arranged as in FIG.3, which is to be described with reference to the vertical addressingbut is equally applicable to the horizontal addressing.

FIG. 3 is a detailed illustration of unit 53 in FIG. 2 which is intendedto operate under the control of tabulating orders issuing, for instance,from the input along with the data to be printed. Each tabulating orderwill include a binary pulse combination which is extended through lines61 to a decoder 60 providing a unique output on one line for any oneinput combination. In the drawing, four input lines `are shown by way ofexample and, therefore, there wil-l be two power four, that is sixteenoutput ilines `62. Each unique'output represents in fact a verticaltabulating order .and is led to a plug connecting board 63 where it maybe cross-connected to any of, say, one hundred and twenty-eight lines 64representing as many possible print-line positions in the printedoutput.

Lines 64 are extended to a vertical address encoder unit 65 consistingof a matrix which produces a binary output on, say,-seven lines66,corresponding to each of lines 64 which has been activated. Thus uponactivation of any one of the one hundred and twenty-eight lines in theconnecting board a binary pulse combination corresponding to the lineactivatedthat is to the print-line selectedis available at the output ofthe encoder. Said output is led to a register 67 in which said binarycombination is set up, the output of the register being in turn extendedto coincidence unit 52 in FIG. 2.

In the above layout, it is clear that, if the tabulating order causes tobe activated any one of the sixteen lines in the vertical encoder unit60 which has not been crossconnected to one of the one hundred andtwenty-eight lines in the connecting board 63, no coincidence will occurin 52, it being naturally assumed that register 67 is timely 1re-set aswill be explained later in conjunction with -a detailed -layout of theoverall system. If vno coincidence takes place, character generation isinhibited in the manner already described with reference to FIG; 2. Itis manifest, therefore, that any data coming through from the inputcalling for an address which has not been plugged up will be ignored bythe system. This means that data conforming to a -certain pre-arrangedtabulating layout will be printed in said `tlayout and the remainderignored. Thus the system is -made capable of a discriminating operationwhich is extremely useful when the output is entered in printed forms,

A further refinement which may be incorporated is the use of a range ofplugged up connecting boards selectable by the system in relation to theparticular form in use. This will he made clear at a ylater stage.

An arrangement similar to that described with reference to FIG. 3 may beemployed for the horizontal tabulating. It is however possible, in thiscase, to adapt the logics toa direct generation of the desiredhorizontal display addresses. In the logics so far described all thecharacter addresses `are gene-rated at all times and tabuzlrating isobtained by inhibiting where printing is not required. When enteringforms, it may well happen that only a few characters are required in anyone line of, say, 128 characters. It is, obviously, an advantage if itcan he arranged for the cathode ray beam to ignore the unwantedhorizontal display addresses and shift directly to the tabulatingaddress which is in fact required,

Referring to FIG. 3, and relating it to horizontal tabulating, it willbe appreciated that the identity of the tabulating address at any onetime selected is carried by the output of the horizontal address encoderforming the counterpart of the Vertical address encoder 65 shown in thefigure. This output may be utilized to impulse register of FIG. 1directly to the binary combination representing the required address, asan alternative to impulsing said register serially from the end stage ofthe sequential pulse generator, as shown in FIG. 1. As a result, thedigital-to-analogue converter such as 31 in FIG. l will produce at anyinstant the output required for deflecting the beam directly to thehorizontal tabulating position called for.

It wil-l Ibe observed, as already indicated in the foregoingdescription, that in any one alpha-numeric word unit to be printed it isthe position of the leading character which is directly generated in the.above manner, following characters in the word unit being generatedstep-wise.

The horizontal tabulating selection is conveniently chosen as apercentage of the character positions in a line. In the exampledescribed with reference to FIG. 3, sixteen different tabulatingpositions both vertically and horizontally are allowed for. Assumingthat the printed record is pre-arranged to have a maximum of one hundredand vtwenty-eight print-lines and as many character positions in oneline, the tabulating facilities described mean that any sixteen out ofthe one hundred and twenty-eight lines or character positions may bepre-arranged for tabulation, the actual sixteen to Ibe operative beingchosen by the way in which the vertical and the horizontal plug boardsare connected up.

Where direct generation of the horizontal tabulating address is employedin the manner described, the coincidence unit 50 of FIG. 2 may bedispensed with since the horizontal address encoder may be adapted todeliver an impulsing output signal directly to register 10 of FIG. 1each time said encoder produces a combination as a result of ahorizontal display address actually plugged up on the board being calledby the input of the system. The coincidence 52 (FIG. 2), on the otherhand, is still required since it is clearly necessary to wait for thedrum 2 of FIG. l to rotate to the position called for before theactuating signal is transmitted. If the drum had no inertia, 'it wouldbe theoretically possible to accelerate it instantaneously to therequired vertical address `by generating an analogue signal in a similarmanner to that described for the Vertical counterpart and utilizing saidsignal to shift the drum through a corresponding angle.

` It will be understood, therefore, that the direct generation of thehorizontal tabulating addresses is made possible by the inertialessnature of the electron Ibeam of the cathode ray tube.

The logics of a practical electronic printer layout which represents afurther embodiment of the system disclosed incorporating the variousfeatures enumerated at page l0 will now be described with reference toFIG. 4.

The printer is arranged to operate on a timing dictated either by theinput medium, through clock or' sprocket pulses issuing therefrom, or bythe printer itself through an internal clock. The rst alternative willbe described rst.

By way of example, it is assumed that the input medium is magnetic tapewith rapid stop/start characteristics, the tape bearing as manylongitudinal tracks as there are bits in the digital code use-d, oneword being represented by transversely aligned magnetic areas, one ineach track. Additionally, the tape is provided with equally spaceduniformly magnetized sprocket areas each coincident with one word. Thetape is passed through a reader which yields sets of data signals, eachset representing one digital word and being generated coincidently witha sprocket pulse. The sprocket pulse determines the instant atwhich theword associated therewith may be handled. The need for this is clearwhen it is realized that the longitudinal tracks are to providedistincton-or-olf magnetic areas requiring a finite spacing therebetween. If aword were to Ibe handled when a spacing occurs, there would be no datasignals produced or, at best, only weak and ill-formed ones w-ouldresult.

In FIG. 4 the data signals on, say, a six-bit code are fed into theprinter on twelve lines forming complementary pairs; binary nought andone to be represented on one and other line respectively of a pair.Sprocket or clock pulses are available on line 101.

In operation, the input is fed in one block at the time, each blockrepresenting the contents of one line of printing. The tape is startedat the beginning of a line and stopped at the end thereof. This meansthat the tape dwells in between lines, but with present day equipmentthe dwell need not exceed a few milliseconds.

The stop-start signals supplied to the reader are made available on line102 in a manner which will become apparent as the description proceeds.It should be noted here however that the timing of said signals isdesigned to take into account the fact that the tape must be in motionbefore it can yield data signals while, due to its inertia, it cannotinstantaneously accelerate to its playback speed or stop immediatelyafter the last word of a block has been read, Thus half an inch or so ofblank tape must be allowed in between blocks.

The input data signals or pulses issuing from the reader are rst read ininto pulse memories 103, one word at a time, under the control of theassociated sprocket pulse. The function of the pulse memories is toensure that the input pulses actually fed to the printer conform to atiming set by the internal clock of the printer when their contents arestrobed.

Pulse memories 103 may be arranged in the form of Hip-flops equal innumber to the digits in the code, six in the present example. Thus, uponreading in, the flipflops will be set each t-o the state cor-respondingto the incoming bit in the digital position to which it belongs. Thesprocket pulse under the control of which the reading in has takenplace, is also effective in changing the state of a bistable 104extending a pulse output to and gate 105 which upon being activated Ibya pulse issuing from dot clock 106 through bistable 107 produces anoutput which in turn operates bistable 108 through a pulse shapingdevice 109. The output of 108` activates and gate 110 -coincidently witha pulse lbeing applied from the dot clock. The net result of thisVsequence of events is that slightly after the occurrence of the sprocketpulse a strobe pulse is generated which is synchronized with the dotclock, or internal clock of the printer, synchronization being ensuredby the and lgates referred to. The strobe pulse forming the output ofgate 110 is extended to pulse memories 103 for sampling the contentsthereof. It is thus seen that the output of the pulse memories is thepulse combination fed in from the reader, said combination however,being made to conform to the printer timing dictated by the dot clock bywhich the sequential pulse generator 111 is governed for thespot-sequential character generation in the manner disclosed forinstance in our copending application Ser. No. 792,128 hereinbeforereferred to. f

Assuming that the combination is character code, the output of the pulsememories 103v through multiple circuits 112a sets up character coderegister 113 which will thus be impulsed t-o the binary combinationcorresponding to the character read into t-he printer. The combinationis extended to character selection matrix 114 which provides as manyunique outputs as there are characters in the range for which theprinter is designed. It is assumed, for the sake of example, that thebinary combination set up in 113 and extended tol 114 is 000001 to whichcorresponds character A. This means that the A character-line inselection matrix 114 will be activated and none other. All thecharacter-lines are fed Vinto a character I'generating network 115cooperating with a sequential pulse generator in the manner described inour copending application referred to. Selection of the A character-linewill therefore mean that the X and Y coordinates required for displayingthe character upon the face of a cathode ray tube as sequence of lightdots will be available in successive X and Y pairs at the output 'of115, the dot formation timing being dictated by the dot clock 106. The Xand Y signals are routed to the deflection means of the cathode ray tubethrough circuits 116 and 117 respectively including amplifiers 118 and119.

The actual instant when generation and display of character A is enabledis determined by a trigger signal to the sequential pulse generator,saidsignal being derived from the output of bistable 108 via bistable120 and gate 121 which is in the activated condition unless disabled.

The electronic switching so far disclosed ensures that upon receipt of asprocket pulse the digital word associated therewith, assuming said wordto be in respect of a character, is made to cause selection of thecharacter to which it c-orresponds and upon selection being performedthe generation and display of the character is triggered olf andexecuted according to a timing set by the dot clock 106.

It has so far been assumed that the output Vof pulse memories 103 -ischaracter code and not order code relating, for instance, to tabulatingorder. Whe-re the output is in fact an order, means must be provided forinhibiting the trigger signal to the sequential pulse generator. rlThisaction is in fact provided through gate 121. The ensuing descriptionwill show that said gate is disabled every time an order has beenrecognized by the logics of the system.

The pulse combination issuing from the pulse memories 103 upon strobingin the manner described apart kfrombeing available on multiple circuits112a is also ,available on a parallel branch thereof 112b whichterminates at :an order decoder unit 122 providing a unique output forany one input combination. The unique outputs are made operative toexecute the orders associated therewith through the logics of thesystem. In FIG. 4

the order decoder has been provided with lseven output sections, asfollows:

12M-Horizontal Tabulating Shift 122b-Vertical Tabulating Shift 122c-LineFeed/ Carriage Return 122d-Figure/ Letter Shift 122e'-Letter/ FigureShift 12M-stop 122g-Blank In order to illustrate the manner in which thesystem is made to discriminate between character code and order code letus assume that the binary combination which will :activate the 122asection of unit 122 has been strobed out .of thepulse memories. Sincemultiple circuits 112a :1 and 112b are in parallel, the combination willbe effective insetting up character code register 113 at the same timeas section 122a is :activated for the execution of a horizontal`vtabulating shiftv order, The setting up of the character code registerwill have no effect, however, if

lthe gate controlling the trigger pulse to the sequential pulsegenerator should be disabled by the time character selection has Ibeeneffected. Disabling is in fact timelybrought about upon activation ofthe 122a section. The output from this section through bistable 123, orgate A124, or Vgate 125, and or gate 126 isV extended to the by thelogics of the system and in particular of the horifzontal and verticaltabulating orders, it should be noted Vthat in the absence of any orderthe printer will produce Y 14 line-by-line printing with indents andword spacing pro duced by simply feeding 000000, or in fact any otherhina-ry combination set aside for the purpose, through the charactercode channel in respect of any character position where printing is notrequired. As in the logics described with reference to FIG. l, the laststage of the sequential pulse generator impulses the horizontaldisplay-address register 127 one step at the end of the generation ofeach character, thus shifting the horizontal printing position one stepas required. As far as line-by-line printing is concerned it is thusclear that the logics of FIG. 1 and FIG. 4 are substantially similarexcept that FIG. 4 includes the logics for drawing information from theinput.

The first major elaboration included in FIG. 4 with respect to FIG. 1 isthe `discrimination between character code and order code.

The description will now proceed in regard to the execution of thehorizontal and vertical tabulating orders in conjunction with pre-settabulating layouts soI as to enable printing `of the decoded characterdata according to any `desired and pre-set layout as required forinstance for entering information upon standard forms.

It was indicated earlier on how the output from section 122a is adaptedto inhibit character generation. Similarly the output from the 122bsection is routed through bistable 128, to Iactivate the common or gate124, the output of which is operative in the manner already described inconnection with section 122er. Gate 124 is provided with a further inputas shown which is also effective in inhibiting character generation.Further reference to this will be included later.

Each vertical and horizontal order comprises two words of the inputcode, one for character inhibition and other functions and the other fordetermining the tabulating address. The first word is effective throughthe order decoder unit 122 in the manner already indicated, and it willbe noted that the character code although present at decoder 122 willnot cause selection of any unique output since the order words areincluded in a diEerent numerical range with respect to the characterwords. Both character and order codes are also extended, on multiplecircuits 112C, to horizontal tabulating signaldecoder 129 and verticaltabulating signal decoder 130. Here again only the order code isefective for the reason stated. In fact only the second word of theorder is operative.

Whether the second word is to be operative in the horizontal lorvertical tabulating atany one instant is determined by whether thehorizontal multiple gate 131 or its vertical counterpart 132 isactivated. It Will be noted that the former cannot be activated unlessit is first conditioned by lan output from section 122m extended throughline 133 and the latter cannot be activated unless it is .conditioned byan output from section 122]: extended through line 134. In addition,each multiple gate requires a further input to ensure correct timing andthis activating input is derived through Abistable 135 and gate 136bistable 137, bistable 135 being set by a sprocket pulse.

Thus, upon strobing yan order out of the pulse memories, the rstsprocket pulse causes inhibition of character generation through thefirst word 0f the order which at the same time conditions either thehorizontal or vertical multiple gate according to the nature of theorder, and the second sprocket pulse activates the conditioned multiplegate through bistable 135, and gate 136 and bistable 137. It will beobserved that and gate 136 is activated upon coincidence between theactuating sprocket pulse and the pulse resulting `from activation ofeither the horizontal or vertical tabulating shift. It is thereforeconcerned with maintaining proper pulse timing. Each time eithermultiple gate is activated character inhibition is ensured through theoutput from bistable 137 being extended to gate 121 through or gate 126.

It should be noted here that unit 129 is the horizontal counterpart ofunit 60 in FIG. 3 and cooperates with horizontal connecting board 140and horizontal address encoder 141 which correspond, respectively, tounits 63 vand 65 in FIG. 3. Similarly for unit 130 vertical connectingboard 142 and vertical address encoder 143, in respect of theircounterpart in FIG. 3. The functioning of units 129, 140 and 141 on theone hand and of units 130, 142 and 143 on the other is the same as thatalready 'described with reference to FIG. 3.

The result of admitting the second Word of the horizontal tabulatingorder to unit 129 is to set up in the digitaltoanalogue converter 138 .asignal proportional to the numerical value conveyed by said second word.This signal applied to the X deflection means of the cathode ray tubethrough line 139 causes the beam of the tube l to shift directly to thehorizontal tabulating position represented bythe number read into unit129.

In the vertical counterpart, th'e result of admitting the second word ofa vertical tabulating order through multiple gate 132 is to set thevertical address register 144 to the numerical Value corresponding tothe line position called for.Y They output of register 144 is extendedto coincidence unit 145 to which the outputof vertical address counter146 Iis also extended. Counter 146 counts the line positions as theyoccur and for this purpose is impulsed by a line start signal appearingon line 147, said signal being derived from the xerographic drum by anyconvenient means at the beginning of each line, said means being forinstance an arrangement for photosensing marks or simply a tachometergeared to the drum. When coincidence exists between the vertical addresscounter and the vertical address register at an instant shortly afterthe commencement of the next line,` and gate 148 is activated, said gatereceiving one input from the coincidence unit and one from the linestart signal. Activation of ygate 148 causes a pulse through thenormally activated for gate 149-the need for which will be explainedlater--to be extended to bistable 150 which is thus unset and sends outa start signal which starts the magnetic tape.

It is clear that while allowing the drum to rotate the angular amountcorresponding to th'e vertical address set up in the vertical addressregister not only must printing be inhibited in the manner described inconnection with the first word-of the tabulating order, but further readout from the input must be prevented, ie., the tape must be stopped.This is ensured by activating and gate 151 which sets bistable 415) andstops the tap'e. Gate 151 is activated, inter alia, when bistable 128 isunset. Bistable 128 is unestonly when a signal appears in the verticaladdress encoder. There vwill be no signal present in the verticaladdress encoder as long as the input does not call for the verticaltabulating address actually plugged up in the connecting board 142.

When, upon the occurrence of the correct vertical tabulating order thevertical address encoder 143 delivers `a pulse which unsets bistable 128a stop tape signal is generated causing bistable 150 to stop the tapeuntil the Vdrum has gone through the correct angle, when the tape willagain be started by a line start signal as described. Since the verticaltabulating shift word is arranged to cause inhibition of all ordersexcept vertical tabulating shift through line 152, provision is actuallyincluded for I allowing the input to pass information to the printeruntil the vertical tabulating address pre-set by means of the connectingboard is called for by the input.

Horizontal tabulating is provided with a similar discriminating action,the horizontal address encoder 141 producing the unset signal forbistable 123. In this case, the need for stopping the tape does notarise since the generation of the horizontal address is instantaneous.The

inhibition -of all orders except horizontal tabulating orders v counter146 may be r'e-set by a page r-e-set signal on line 154 derived in anyconventional manner.

The horizontal address register 127, on the other hand, would normallyre-set itself on the n'ext binary step following llllll-a six-bit codebeing still assumed by way of examplebut an additional `re-set isprovided in connection with the Line Feed Carriage Return order as willbe presently described.

From the foregoing description it is clear that the element whichfinally controls the starting and stopping of the tape system isbistable 150. It is also clear that it is not possible eifectively tostart the syst'em at any random yinstant by manual oper-atiombut only atthe instant when -coincidence is in fact occurring in unit 145. A manualsignal on line 155 is thus arranged to condition and gate 149 throughbistable 156, and gate 149 being activlated to unset bistable 150 andgive vthe effective start signal only upon coincidence occurring in 145.Assuming that coincidence is about to take place, the actual timing ofthe effective start signal is determined by the line start signalavailable on line 147. l

The operation of the remaining orders included in sections 122c and 122gof the order decoder 122 will now be described.

Section 122e` is reserved to the Line Feed-Carriage Return order, asalready indicated. The need for this order arises where no tabulationorders are given to the system. In other words, the printing has beenallo-wed to proceed to the end of one line and the next line is to beprinted in the succeeding vertical position. It is clear that the LineFeed part of the' order must be effective in stepping the verticaladdress register 144 one step while the Carriage Return part of theorder -must be simultaneously effective to re-set the horizontal addressregister 127 to zero as required for starting a new line. Two furtherrequirements which must be met, also simultaneously, is to inhibitcharacter generation and to stop the tape. For conveying the Line Feedsignal a connection is provided, as shown, between section 122e andvertical address register 144. This connection is lfurther extended tohorizontal address register 127 since the same signal executes theCarriage Return order. The other two requirements are met as follows:character inhibition, through bistable 157, or gate 158, or gate 126,the latter inhibiting gate 121, which, as we have seen, controls thetrigger pulse to the sequential pulse generator 111; stopping of thetape is achieved through connection to or gate 151, the action of whichhas already been described.

When the above order has been executed and the drum has advanced asufficient amount coincidence will occur in as the line start signalfrom 145 is delivered. This ,signal issuing fromA 145 as coincidencetakes place `effec- "tional stage-not shownof the character coderegister 113. As a result the number of characters which may be selectedfrom a given input is doubled. A five-'bit code with the above shiftfacilities is almost equivalent to a six-bit code without saidfacilities. As with other orders, simultaneous inhibition of charactergeneration is necessary, and this is arranged through or gate 160,bistable 161, or gate 125, or gate 126, control gate 121. Bistable 161is re-set through bistable 135 actuated by a sprocket pulse or, as weshall see presently, from a pulse of the internal clock to be described.

Section 1221" is provided for the execution of the Stop order. Suchorder must obviously fulfill only two requirements: inhibit charactergeneration and st-op the tape.

The rst is met through bistable 156, or gate 158, or

17 gate 126, and control gate 121; the second, through or gate 151 andbistable 150.

ySection 122g conveys the Blank order which allows the tape to runWithout any character being displayed. In the present embodiment acombination such as 000000 activates section 122g which simply inhibitscharacter generation through or gate 160, bistable 161, or gate 125, org-ate 126, and control gate 121.

The system is in addition provided with a further order which comes intouse when the variable information issuing from the tape is to be printedin superposed relation to standard information which may be selectivelyoptically projected upon the xerographic drum. A case in point is wherevariable information is to be entered in any of ,a range of standardforms which may be stored as photographic transparencies adapted to beselectively projected onto the drum. The further order referred to-is`in fact a Change Form order and enables selection of the transparencyat any one time required.

Similarly to the tabulation orders, the'Change Form order comprises twowords of the code in use. One word, elfective on multiple circuits 112d,causes bistable 162 to be set. The output of bistable 162 is extendedthrough or gate 124 to or gate 125, or gate 126, and control gate 121,and at the same time conditions multiple gate 163 which upon receivingan output from bistable 137 when the latter is impulsed by a sprocketpulse through and gate 136 and bistable 135 allows the second word ofthe Change Form order which is effective on multiple circuits 112e to beread through to set of bistables 164 to 168 exclusive. Said bistablesstore the binary coding marking the form selected. The second word ofthe order conveys in fact the binary number by which it has beenarranged to identify a given form. The output of the bistables are sentto a form selection decoder 169-for instance, a simple relay-tree typeof decoder-which :at any one time yields a unique output marking theform selected. The unique output may then be used to select 'thecorresponding transparency.

Should` the order to change formV arrive half-way through the`completion of a form, it is obviously necessary to inhibit theform-selection decoder 169 until an end of vform signal is available/'online 170 derived from the transparencies carrying member which isconveniently arranged, for instance, as a rotatable transparent cylinderilluminated from within androtating at a speed bearing a convenientrelation to the speed of the xerographic drum, selection of thetransparency required being effected =by selectiveoperation of lightshutters in conjunction with v an opportune optical system.

Since the Change Form order wouldnormally be associated with printingaccording to pre-set tabulating layouts as arranged through connectingboards 140 and 142 in the manner hereinbefore described, the re-settingpulse for bistable 162 is conveniently derived from the rst verticaltabulating lorder following form change. Thus section 122b of the orderdecoder 122 is shown connected to bistable 162.

The Change Form order may additionally be made to control the selectionof the pair of connecting boards required for the form chosen. Aswitching relay may for instance lbe incorporated either preceding orfollowing units 129 and 130.

A number of pulse shaping devices have been shown in the functiondiagram of FIG. 4. A pair of pulse shaping devices 171, 172, are shownin connection with the horizontal and vertical tabulating shift. Another173, is shown inserted in the path of the line start signal to and gate148. Still another 174 in the re-set path of bistable 137.

. A number of delay units such as 175 and 176 on the line start signalcircuit have also been included. Both pulse Shapers and delay units donot perform logical functions but merely ensure correct handling andtiming of pulses.

A line break register 183 is the counterpart of-stage 40 in FIG. 3 andit is intended to enable two lines of characters spaced vertically uponthe screen of the cathode ray tube to be combined in one line on thexerographic drum by a suitable optical arrangement.

In the foregoing description relating to FIG. 4 it has been assumed thatthe system is controlled through the sprocket pulses issuing from theinput medium, which,

by way of example, has been given as magnetic tape. This entails upperand lower limits of reading-in rate. The tape must be neither fasterthan the repetition rate of the character generator allows nor slowerthan the minimum which will permit a line full of characters to bedisplayed.

The system illustrated in FIG. 4 actually includes provision for afurther mode of operation selectable by throwing switch 177 over to theposition shown in dotted line. This second alternative is based on theaction of an internal pulse clock represented by elements 104, 105, 109,108, 120, and gate 178 or gate 179, pulse shaper 180 which form a closedloop. The internal clock is used in conjunction with an input bufferstorage (not shown) in which the signals from the tape are read in andfrom which they can be read out in an on demand fashion, thus allowing agreat volume of information not conforming to predetermined tabulatinglayout to be rejected rapidly, in fact at a rate far exceeding therepetition rate of the character generator.

The internal clock is arranged to be pulsed into action under thefollowing circumstances: (a) when a line-start signal is given; (b) whenthe horizontal tabulating yshift bistable 123 is re-set; (c) at the endof one cycle of the sequential pulse generator where charactergeneration has not been inhibited. The initiating pulse, whatever theorigin thereof is delivered through or gate 179 and the connections areclearly shown in the diagram. The initiating pulse originating frombistable 123 passes through a pulse delay device 181. Whether the clockwill go through repetitive cycles or not, is determined by and gate 178which is adapted to be activated through or gate 125 when any one ofsections 122a, 122b, 122d, 122e, 122g or change form -orders areoperative. And gate 17 3 controls the break in the closed loop referredto. When the loop is broken a further initiating pulse through 179 isrequired to activate the internal clock.

In general the loop will not be broken when information is beingrejected because it does not conform to predetermined tabulatinglayouts. In fact, as .long as this condition persists bistables 123 and12S will not be reset from the horizontal and vertical address encoderrespectively, gate` 125 is activated, which in turn maintains loopcontrolling gate 178 operative.

The repetitive rate of the loop obviously determines the speed at whichthe information is being rejected, and this can be made quite high-say50 kc. for a S-kc. character speed.

At each cycle of the loop a store read action pulse must be producedtherefrom. In FIG. 4, said pulse is the output of bistable 108 and isavailable on line 182. Its action is to cause a set of pulses to begenergated from the input buffer storage which will be read into thepulse memories 103 and handled by the system in the manner alreadydescribed. l

Here is a summary of the actual sequence of operations. A pulse fromgate 149 representing a line start causes gate 17 9 to deliver aninitiating pulse to the clock. After a short delay determined by thetime constants of the clock elements a store read action pulse will beavailable on line 182 to read out from buffer store into pulse memories103. After a further delay, a digit strobe pulse will issue from gate tosample the pulse memories and to set up character code register 113, asalready indicated in the foregoing description. After a still furtherdelay, bistable will produce an input pulse activating gate 121 whichtriggers the sequential pulse generator 111 into action and causes thedisplay of the character stored in register like references -in FIGURES1 and 5.

113. If the input is order code instead of character code, one of thesections of the order decoder 122 is activated, or the change form orderis operative.V Out of the decoder sections shown in FIG. 4 the Line FeedCarriage Return section 122C and the Stop section 122f must obviously bearranged to cause character inhibition but no further read out; they aretherefore effective in inhibiting the gate to the sequential pulsegenerator but have no action on the loop control gate 178. As regardsthe Stop order, the reason for this is obvious. As regards the Line FeedCarriage Return order, the reason is that the reading in of the nextblock of information must be initiated by a line start signal. `On theother hand, sections 122a and v122b must both be allowed to initiate theclock as soon as the -correct tabulating orders have been recognized,while sections 122d and 122g involve an initiation pulse directly uponactivation thereof. These latter three sections therefore cooperate witha communal or gate 160.

At this stage the logics of the gating arrangements shown can be clearlyunderstod by the skilled in the art. It will be observed in particularthe separate function of gate \125 enabling loop closing pulses to bedelivered to gate 178 from decoder sections involving said pulses, andof gate 126 whichgroups together the action of character inhibitionpulses only, which are effective in disabling gate 121.

The loop hereinbefore referred to need not be necessarily arranged asshown, there being alternative ways of producing the clock pulses withthe required timing. The essential fact is that as far as read out isconcerned the system has been provided with both high read out rate,through the internal clock, or low read out rate under the control ofthe sprocket pulses which may be taken as constituting an externalclock.

The foregoing description of the embodiment illustrated I in FIG. 4clearly indicates that a system has been ldevised whi-ch accepts bothcoded alpha-numeric data and coded orders, `and discriminatesbetweenthem in the sense that alpha-numeric data is displayed successivelyunless an order is received, whereupon character generation isinhibited, the order executed, and further read out from store effected.

The arrangement described in FIG 5, which as indicated earlier on iscommon to all foregoing embodiments, will now be described.

For a clearer understanding like parts have been given Thusy axerographic drum 9 is shown in spaced relation with a cathode ray tube2, the deflection means of 'which are supplied `with X and Y deflectionwaveforms fed through amplifiers 4 and 3. ri`he deflection means, as inany other embodiment, may be of the electrostatic or elect-romagnetictype.

The display of characters on the screen of the cathode ray tube isadapted to be projected upon the drum through a lens system indicatedd'iagra-rnmatically at 8. The drum is geared to a tachometer 12.

Assume that a line-up of characters displayed on the screen is to beprojected onto the surface of the drum in ray tube, this relativemovement between displayed character and drum would result in a line ofcharacters being printed askew instead of at right angle to thedirection of motion of the print receiving medium, say, a paper webtransported from one feed to one take up roller.

The means for counteracting said relative movement according to FIG. 5consists in feeding a rate signal derivd from tachometer 12 into an`integrator 200 -see also FIG. 4--givin-g an output rising linearly from`a datum value toa maximum, which is reached after a given number'oftachometer pulses Ihave occurred, with a slope ultimately governed bythe rate at which these pulses are forthcoming. After the maximum hasbeen reached the output is adapted to fall back to the -datutm levelvery rapidly in saw-tooth fashion. The integrator output is fed to the Ydeflection means of the cathode ray tube through Y amplifier 3. K

Integrator 200 is adapted to be controlled by` the line start signal online 201, the derivation of which has already been indicated in theforegoing description.

In operation, when a line start signal is -fed to the in tegrator thefirst character of a line-up is displayed. The first character obviouslyinvolves no Y shift and, therefore, it is made to correspond to thepoint where the integrator output is about to rise from the datum level.By the time the second character is displayed, the drum Will have movedby a very small amount and Y shift is therefore required proportional tothe rate of the movement. Similarly in respect of subsequent charactersin the lineup, until the last character is displayed whereupon maximum Yshift is required. It is seen therefore that said shift is effective ina number of steps which must be equal to the maximum number ofcharacters in a line-up, the height of each step being proportional tothe rate at which they occur.

The tachometer is, therefore, adapted to yield a number of pulses equalto the maximum number of characters in the line-up per angular movementof the drum corresponding to the height of one character.

Having arranged matters so that the integrator output provides therequired correction at a given speed, the correction will increase ordecrease in step with a similar variation of drum speed.

It will be observed that the arrangement is independent of `the incomingrate of yinput signals. In fact, it is independent of the rate at whichcharacters are displayed upon the screen. Whether the rate of display ishigh or low, Aas long as characters appear on the screen they will beprinted in slant-free fashion at any drum speed.

The speed of the drum may be easily controlled in relation to printingrequirements thus lending considerable versatility to the printer as awhole.

The foregoing description relating to both t-he embodiment-s of FIG. land FIG. 4 clearly lindicates that the logics olf the electronicprin-ter allow characters to be posted or addressed independently Vofthe input signals which identify them. In fact the only function of thecharacter code, or display producing signals, is to select` a circuitwhich activates the generation of the correspond'- ing character. Thecharacter code in no Way affects the position in which a character is tobe printed nor in fact the timing.

Reverting for instance to the embodiment 'of FIG. 1` and examining thecondition obtaining in line-by-line print-l ing with word spacingcontrolled through a predetermined input word set aside for thispurpose, it will be observed" that the opposite or display address ofsuccessive charac-` ters is generated through the action of a pulseemerging from the last stage of the sequential pulse generator, whichpulse shifts .the horizontal address register one binary step, while thesequential pulse generator is triggered into afurther cycle unlesscharacter inhibition is operative, the further cycle causing at theendthereof the lgeneration of a successive horizontal address. Thus eachsuccessive horizontal display position with the exception of the firstposition in la line-which corresponds to rest conditions-is determinedby a device which is timed independently of the character signals. Infact, the sequential pulse generator sets the instant when a charactermay be accepted from the input through character code set up timing.This means that the maximum rate at which characters may be displ-ayedis set by the character repetition rate and not by the rate at whichcharacter signals are forthcoming.

Similarly when tabulating facilities as described are made use of. Thetabulating orders are in fact operative only in determining thehorizont-al and vertical address of the first character in a group ofcharacters, the horizontal address `of following characters beinggenerated as before through the step-wise action caused by thesequential pulse generator independently of the input character code.

It should be further observed in relation to FIG. 4 wherein means areincluded for discriminating between character code and order code, thatsaid means are interposed only between the input and the means fordetermining the position where given items are to be printed. In theexample shown the discriminating means is provided by the order decoder.There is not -included any such means between the input and thecharacter generator. So much so that in fact any input word whethercharacter code or order code is read into the character generator but isnot effective if the order decoder has recognized such word as an ordercode.

In the foregoing description a number of well known devices have beenreferred to. Most of these have been described in detail in, DigitalComputer Components and Circuits, by R. K. Richards, published by VanNostrand and printed in the United States of America. Thus the bistablesreferred to are of the type as for instance described from page 160;similarly, page 57 in respect of decoders and encoders; page 38, forgates; page 171 for monostables, page 486 for the integrator.

As regards the sequential pulse generator, this may be arranged as aseries of flip-flops wherein each stage with the exception of the firstis pulsed into action by the preceding stage. A more elaboratearrangement particularly suitable for the realization of the inventionis that disclosed in British Patent lNo. 766,987.

I claim:

1. In a system for recording a first character array composed of one ormore lines of variable characters in superposed relation upon a secondcharacter array composed of a plurality of lines of a iixed arrangementof such characters for subsequent printing out of the characters of botharrays in their proper relative positions, the combination comprising,means providing a signal input character code characteristic of thevariable characters desired to be recorded, a character generatorcontrolled by said input character code for producing the desired Ycharacters in code form and in'a sequential manner, means connected tothe output of said character generator for converting the code form ofsaid sequentially produced variable characters into one or more lineimages in a lineby-line manner in accordance with the signal inputcharacter code, means establishing said second character array as astandard image and projecting lthe same in a line by line manner onto alight-sensitive surface which moves in a direction transverse to thedirection of the projected lines of characters iof said second characterdisplay, means for also projecting the line images of said variablecharacters of said first character display in a line-by-line manner ontosaid moving light-sensitive surface in the same transverse direction assaid character lines of said second -character display are projected,means establishing vertical and horizontal recording addresses and meansactuated by said vertical and horizontal recording addresses forcontrolling respectively the production of said line images of saidvariable characters and the horizontal position of the characters on theline such that said line images will be superimposed according to apredetermined layout upon the projected line images of said secondcharacter display.

2. A recording system as dened in claim 1 and which further includesmeans establishing a store of `different standard image forms, meansestablishing `a change form order code, and means controlled by saidchange order form code for selecting a particular one of said standardimage forms from said store for projection onto said movinglight-sensitive surface.

3. A recording system as defined in claim 2 and which furtherincludesmeans providing sets of predetermined tabulating signal combinationscorresponding respectively to each standard image form, said signalcombinations serving to effect removal of the desired standard imageform from said store and in turn being selected by said change formorder code.

4. A recording system as defined in -claim 1 wherein said means forlconverting the code form of said variable characters produced by saidcharacter generator into one or more line images for projection ontosaid moving lightsensitive surface is constituted by a cathode ray tubehaving X and Y axes beam deecting means for creating the character onthe screen of the tube.

5. A recording system as defined in claim 4 and which further includesmeans for deflecting the characters produced on the screen of sa-id tubeby a signal independent of the incoming rate of the signal input codebut which is proportional to the `distance travelled by saidlight-sensitive surface so as to maintain the line of sequentiallyproduced variable characters projected onto said moving light-sensitivesurface transverse to the direction of movement. v

6. A recording system as defined in claim 5 wherein said signal fordeflecting said characters comprises a signal having `a saw-tooth waveform applied to the Y-deflection axis of said tube to compensate for theline slant that would otherwise be produced at said movinglight-sensitive surface.

7. A recording system as defined in claim 4 wherein said variablecharacters displayed on the screen of said cathode ray tube are composedof a succession of light dots and wherein the simultaneous X and Y axisdeflection wave forms required at said tube are gated to said tubedirectly upon generation caused by a sequential pulse generator.

8. A recording system as defined in claim 1 wherein said movinglight-sensitive surface onto which said images of said first and secondcharacter displays are simultaneously projected in a line-by-linem-anner is constituted by a xerographic recording surface.

9. A recording system as defined in claim 1 wherein said signal inputcharacter code is established on a recording medium such as magnetic orperforated tape, the signals :being fed into the system at a ratecontrolled by signals issuing from said recording medium.

1t). A recording system as defined in claim 1 including means derivingsaid input signal code Via a recording medium via a buffer store, saidsignals being read out of said store into the system and beingcontrolled by a timing set by the system.

References Cited by the Examiner UNITED STATES PATENTS 2,648,723 8/ 1953Goldsmith 3404-149 2,785,388 3/1957 McWhirter et al. 340-149 3,187,094k6/1965 Giles 178-6.8

NEIL C. READ, Primary Examiner. T. A. ROBINSON, Assistant Examiner.

1. IN A SYSTEM FOR RECORDING A FIRST CHARACTER ARRAY COMPOSED OF ONE ORMORE LINES OF VARIABLE CHARACTERS IN SUPERPOSED RELATION UPON A SECONDCHARACTER ARRAY COMPOSED OF A PLURALITY OF LINES OF A FIXED ARRANGEMENTOF SUCH CHARACTERS FOR SUBSEQUENT PRINTING OUT OF THE CHARACTERS OF BOTHARRAYS IN THEIR PROPER RELATIVE POSITIONS, THE COMBINATION COMPRISING,MEANS PROVIDING A SIGNAL INPUT CHARACTER CODE CHARACTERISTIC OF THEVARIABLE CHARACTERS DESIRED TO BE RECORDED, A CHARACTER GENERATORCONTROLLED BY SAID INPUT CHARACTER CODE FOR PRODUCING THE DESIREDCHARACTERS IN CODE FORM AND IN A SEQUENTIAL MANNER, MEANS CONNECTED TOTHE OUTPUT OF SAID CHARACTER GENERATOR FOR CONVERTING THE CODE FORM OFSAID SEQUENTIALLY PRODUCED VARIABLE CHARACTERS INTO ONE OR MORE LINEIMAGES IN A LINEBY-LINE MANNER IN ACCORDANCE WITH THE SIGNAL INPUTCHARACTER CODE, MEANS ESTABLISHING SAID SECOND CHARACTER ARRAY AS ASTANDARD IMAGE AND PROJECTING THE SAME IN A LINE BY LINE MANNER ONTO ALIGHT-SENSITIVE SURFACE WHICH MOVES IN A DIRECTION TRANSVERSE TO THEDIRECTION OF THE PROJECTED LINES OF CHARACTERS OF SAID SECOND CHARACTERDISPLAY, MEANS FOR ALSO PROJECTING THE LINE IMAGES OF SAID VARIABLECHARACTERS OF SAID FIRST CHARACTER DISPLAY IN A LINE-BY-LINE MANNER ONTOSAID MOVING LIGHT-SENSITIVE SURFACE IN THE SAME TRANSVERSE DIRECTION ASSAID CHARACTER LINES OF SAID SECOND CHARACTER DISPLAY ARE PROJECTED,MEANS ESTABLISHING VERTICAL AND HORIZONTAL RECORDING ADDRESSES AND MEANSACTUATED BY. AND VERTICAL AND HORIZONTAL RECORDING ADDRESSES FORCONTROLLING RESPECTIVELY THE PRODUCTIODN OF SAID LINE IMAGES OF SAIDVARIABLE CHARACTERS AND THE HORIZONTAL POSITION OF THE CHARACTERS ON THELINE SUCH THAT SAID LINE IMAGES WILL BE SUPERIMPOSED ACCORDING TO APREDETERMINED LAYOUT UPON THE PROJECTED LINE IMAGES OF SAID SECONDCHARACTER DISPLAY.